1. Field of the Invention
The present invention relates to an inverter control device whereby, when the connection between a battery and a smoothing capacitor is disconnected, the charge that has accumulated on the capacitor is discharged and an electric vehicle using this control device.
2. Description of the Related Art
In a construction in which a motor is driven by an inverter using a battery as the power source, when operation of the motor is stopped, the connection with the smoothing capacitor is usually disconnected, in order to minimize battery consumption to the greatest possible extent. However, since, at this time point, charge will have been accumulated on the smoothing capacitor, it is desirable that this accumulated charge should be rapidly discharged.
Discharge of the smoothing capacitor as described above is performed by connecting a discharging resistor to both terminals thereof but this leads to the problem that providing a discharging resistor makes the overall size of the inverter large. As a technique for solving this problem, Laid-open Japanese Patent Publication No. H.9-70196 discloses a construction in which the charge accumulated on the smoothing capacitor is discharged without driving the motor by making the torque current component Iq zero and by making the exciting current component Id a prescribed value, in vector control of the motor that is used for driving the electric vehicle.
With this prior art, if it becomes impossible to obtain an output signal from the rotary position sensor or current sensor, as for example in the event of an accident or malfunction, there is the risk that it may become impossible to perform discharge as desired or, indeed, discharge may become completely impossible.